2009 Mercedes-Benz ML320 Bluetec Follow-Up Test

We hope you're not in a hurry.

During our track testing, the 2009 Mercedes-Benz ML320 Bluetec diesel reached 60 mph from a dead stop in 8.5 seconds. If you're planning to rob a bank, the new ML320 can hold a lot of loot, but it won't help you make a quick getaway.

If it's long-distance cruising range you're after, however, Mercedes says its diesel-powered 2009 ML320 can run for 600 miles on a single tank of fuel. The coppers will get way tired before you have to fill up again.

Of course, you'd probably rather make a great escape with the kinfolk. So for the statistical American family of mom, dad and two-and-a-half kids, the 2009 Mercedes-Benz ML320 Bluetec represents a five-passenger family SUV that's a miracle of thriftiness at the fuel pump and won't leave a tell-tale trail of smelly grit behind you.

Going Green With the Blue Juice
A diesel gets 20-30 percent better fuel mileage than a gasoline engine, but it has a reputation for being a noisy, dirty, smelly thing. So up until now, a diesel-powered vehicle has forced us to make a choice between pocketbook-friendly transportation and environmentally friendly transportation. And once strict environmental standards for passenger vehicles were instituted, you couldn't buy a diesel car in every state in any case.

But now that ultralow-sulfur diesel fuel is finally widely available in America, the European manufacturers are bringing us their latest emissions-friendly diesel vehicles. So now you can go green without buying into a battery-operated hybrid.

The Bluetec diesel system is technology developed by Mercedes-Benz to reduce oxides of nitrogen, the diesel's distinctive air-emissions signature. It requires the use of AdBlue, a trademarked reducing agent that is injected into the exhaust, converting nitrogen oxides into nitrogen and water in a downstream catalytic converter. The AdBlue needs to be refilled as part of the vehicle's regular maintenance schedule, about every 10,000 miles. It doesn't have to be filled by a Mercedes dealer, however.

If you run low on AdBlue, the vehicle warns you that you have sufficient fluid for only a limited number of engine start-ups, beginning at 20. If you neglect to refill the AdBlue, the engine will eventually refuse to start. The special seven-gallon tank is situated under the rear cargo area where there would normally be a spare tire. (That's why the ML320 Bluetec comes with run-flat tires, not our favorite choice.) According to Mercedes, Bluetec technology makes this Mercedes diesel engine as clean-burning as a modern gasoline engine; therefore it can be sold in all 50 states.

The ultralow-sulfur diesel fuel (97 percent less sulfur) helps complete the clean-air equation by making things easier on the particulate filter.

Speak Up. We Can't Hear You
As diesels go, the 2009 Mercedes-Benz ML320 Bluetec is fairly quiet. There is a low diesel rumble when you put your foot down, but it can easily be drowned out with music (ah, thank you, modern technology). If you want to be alone with your thoughts or like to drive with the windows down, you'll just have to get used to it. It's not loud and obtrusive, but it is there, like the low vibrato of a contralto.

The ML320's 3.0-liter V6 diesel engine features a lightweight aluminum block, a forged-steel crankshaft, cylinder heads with four valves per cylinder, and an internal balance shaft to control the vibration created by the diesel's tall 16.5:1 compression ratio. A variable-nozzle turbocharger spins quickly to reduce turbo lag and then helps deliver 210 horsepower at 3,800 rpm and 398 pound-feet of torque at 1,600-2,400 rpm.

The diesel V6 is mated to a quick-shifting seven-speed automatic transmission with the same column-mounted shift lever you'll find in the Mercedes R-Class, although there are also shift paddles mounted on the steering wheel. With seven gears, programming for maximum fuel-efficiency, a relatively narrow power band and a redline of only 4,500 rpm, the transmission always feels full of activity, but it's smooth and quick to react at least.

Diesel Performance
In normal city driving, the ML320 Bluetec's powertrain had plenty of power, although it didn't really develop any urgency until the torque peak came within reach. At the test track, where we try to ring out every precious second, the ML320 would launch like a Nissan GT-R and achieve 30 mph in a heartbeat, but then it would realize that such behavior is unseemly for a turbodiesel and finally reach 60 mph in 8.5 seconds (8.2 seconds with 1 foot of rollout like on a drag strip). It hit the quarter-mile in 16.2 seconds at 83.3 mph.

Of course, we can't drag race like this at every traffic light, so we must admit that in everyday driving we found the ML320 Bluetec to be a little slow. We had no problems getting up to speed on freeway on-ramps or while passing on the highway. It was just that laziness after 30 mph that bothered us.

Meanwhile the ML320's 13-inch disc brakes prove pretty effective with the relatively wide 255/50R19 Bridgestone Dueler H/L 400 tires and helped bring this 5,129-pound Benz to a halt from 60 mph in 121 feet. The brake pedal feels mushy underfoot as if it's not really connected to anything; nevertheless, there's plenty of stopping power and very good resistance to fade.

Floats Like a Butterfly
The 2009 Mercedes-Benz ML320 diesel waltzes through our slalom course at 62.6 mph; a darn good number for an SUV that is 71.5 inches tall and weighs 5,129 pounds. The latest iteration of Mercedes' stability control gives you greater leeway for enthusiasm before the electrons intervene, and it's tuned almost perfectly for the ML so the limits of the chassis are reached right when the stability control does its stuff.

As a result, the electrons intervene only if you're sloppy; stay smooth and they mind their own business. And there's a good amount of grip to work with, as the ML attains 0.76g on the skid pad.

Strangely enough, this ML doesn't feel nearly as sure-footed in everyday driving, as the optional Airmatic air-spring suspension conspires to make this Benz seem soft and wobbly on the highway, as if it were even taller than 71.5 inches. Even though we cycled through three damping settings — Comfort, Sport and Regular — life still proved a little too buoyant for the stomachs of our passengers.

All-Terrain Mobility
As ever, the ML's all-wheel-drive system takes full advantage of its ABS electronics to maintain traction, a strategy that Land Rover and Toyota have adopted now that the system can react so quickly and reliably.

So as a result, the Mercedes 4Matic all-wheel-drive system delivers not only full-time all-wheel drive but also four-wheel traction control, a downhill speed regulator, and a hill-hold function that works both uphill and down.

One of the virtues of the optional air suspension package is its ability to automatically adjust ground clearance. It compensates for high or low speeds on its own, and a switch on the dash can be used to manually adjust the vehicle height by more than 3 inches, providing 10.5 inches of ground clearance.

Another Look for Benz
This is the least Mercedes-looking Mercedes. The ML320 could be any other large SUV, especially in profile. Even though Mercedes has redesigned the front and rear bumpers, changed the headlights and put on a larger and lower grille, the ML320 comes in at the same size as last year's CDI. Our tester was coated in Alpine Rain metallic paint, a fancy name for gray, which put an additional $720 on the bill and succeeded in enhancing the visual blandness.

While its exterior may be ordinary, once we slipped inside the ML320, we knew we were in a Mercedes. Even the plastic bits on dials and switches were sturdy and moved with a polished finish that you'd expect from a luxury carmaker. A new four-spoke steering wheel featured fingertip controls for audio and the information center. The burl wood trim was unmemorable but the light cashmere-colored leather added a rich look and feel.

The interior was jam-packed with features such as a rearview camera, navigation, voice control, push-button start and more. These tallied up to more than $10,000 in elective equipment and pushed the sticker over $60K. Good thing you'll be saving money on infrequent fill-ups.

Diesel No More
EPA estimates for the ML320 Bluetec are 18 mpg city and 24 mpg highway. We averaged 21.2 mpg during our time with the vehicle. Fuel tank capacity is just a smidgen over 25 gallons, so you can realistically get up to 500 miles on one tank of mixed driving.

Mercedes has made diesel normal. If you're looking for an alternative to a hybrid or just a roomy SUV, the ML320 Bluetec has made the diesel-y things that go along with a diesel as unobtrusive as possible. It burns clean, it's a lot less noisy and it doesn't smell.

The 2009 Mercedes-Benz ML320 Bluetec is a normal SUV. Just make sure you go to the right pump.

The manufacturer provided Edmunds this vehicle for the purposes of evaluation.